Can someone give me some quick help on reading a dial indicator? Just got through with the precision measuring lecture today in school, and have some work sheets to do with different dial face pictures, where I have to give the reading. Only thing I'm having trouble with is when the dial is pre-loaded. I have worksheets with both 0.100 and 0.200" preload. If the dial is reading 0.155", would I add the 0.100 preload, or subtract it?

I would say that as long as you are measuring some kind of of travel that only pushes towards the indicator,, you would subtract the preload amount to get your true measurement of travel.
(I don't want to get caught in some kind of trick question...)

i thought this earlier but did not post, but i will post for the sake of arguement in response to mikey's post.

sounds like a trick question to me--you always preload a dial indicater and spin the face to "o" the pointer, then read the needle movement. so if the needle movement is .019, .190, etc. that is what it is--you don't subtract the preload. besides, who would set the preload at exactly .100, .200 or whatever. whats the point???

Here is my guess, techron, I always zero the dial too, but I think he may be referring to the little rotation or "rev" counter being preloaded.
I never been schooled proper in anything, (grammar included), but I'd imagine that in a NTMA class they'd teach you how to read the indicator using all of its graduations and counters. Just like reading a clock....the big hand is on the .012 and the little one is on the 2...so that means .212"...now if your revcounter was set on .1, and you zeroed the dial, and your actual readout was .155", then your travel was really.055".

(I have a dial indicator manufactured by Oldack that reads exactly like a clock, with a big and little hand mounted in the center.)

So where you and I might just preload the indicator on an arbitrary spot , zero the dial, then start counting sweeps of the needle until it stopped,, a machinist would need to be able to tell you what the travel was just by looking at the 2 hands on the dial.

Many times in a machine shop enviorment, the big needle will swing too fast to see and count the revolutions, so the rev counter is the only way to know for sure.

ah, that makes sence, i've seen those, i didn't read/think of it that way. i use 2 starretts, they are pretty old and don't have the rev counter, i just watch how many times the needle goes around (if applicable) like checking valve lift. the starretts i have are very nice, they come in an old time red leather covered hinged hard case for each one with all the little setup goodies. one has a biger dial and more travel than the other. the OPs wording of the question wasn't real clear to me.

I wasn't trying to measure anything. Like I said in my original post, I just had some worksheets to do. All I had was a page with six pictures of dials, and I had to write down the correct reading. One sheet had a .100 preload, and the other had a .200 preload. I got it figured out though.

I wasn't trying to measure anything. Like I said in my original post, I just had some worksheets to do. All I had was a page with six pictures of dials, and I had to write down the correct reading. One sheet had a .100 preload, and the other had a .200 preload. I got it figured out though.

glad you got it figured out. i think what has us confused is the termonoligy "preload". .100 is one sweep of the dial, .200 is 2 sweeps of the dial. this is not "preload", it is part of the reading on the dial. "preload" would be the starting point of the plunger. anyway, glad you figured it out. isn't asking us cheating???

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